|  | 2.3 | Switching and VLANs
| 2.3.2 | Ethernet switch latency
Each switch used on a 10 Mbps Ethernet LAN adds latency to the network. However, latency depends on the brand of the switch and upon the type of switching used. As will be explained later, the different switching modes ("store and forward", "fragment free", and "fast forward") differ on when the decision to switch an incoming frame is made. The latency due to the switch "making its decision" must be added to the time for the frame to enter and exit the switch ports and determines the total latency of the switch. Note that a hub, which is simply forwarding frames (with no filtering or decision-making), has only a port-to-port latency. All of these fractions of a second may not seem to matter much, but recall that we are sending data a rates of 10 Mbps (1 bit per 1 ten-millionth of a second), 100 Mbps (1 bit per 1 100 ten-millionth of a second), or 1000 Mbps (1 Gbps, 1 bit per 1 billionth of a second). So networking devices are operating at incredibly high speeds, so every nanosecond can matter!